Teach pendant control method and device

ABSTRACT

There has been a problem that in the operation of a teach pendant having two enable devices (3-position switches) on the right and left sides, shifting it from one hand to the other results in prohibition of operation. In that operation is made possible until a predetermined time elapses even if the 3-position switches are operated by both hands in shifting the teach pendant from one hand to the other, shifting it from one hand to the other is allowed, making continuous operation of the teach pendant possible, while ensuring security in that when the time of operation with both hands exceeds the predetermined time, operation is inhibited.

TECHNICAL FIELD

The present invention relates to a control method for a teach pendantused for a manipulation for teaching an operation to devices such asindustrial robots or machine tools, and more particularly to animprovement of a control method for permitting or inhibiting theoperation of the device by a teach pendant.

BACKGROUND ART

Usually, in the production line of a factory, many industrial robots forautomatically performing a welding operation, an attaching operation ofparts, a conveying operation or the like are employed. Prescribedoperations are previously taught to the industrial robots by exclusiveteach pendants and the robots perform various kinds of operations byreproducing the contents of teaching. The teach pendant is alsoordinarily referred to as a teach device. A similar teach pendant isused for teaching (program) working procedures of various kinds ofmachine tools, NC machine tools, etc.

A teaching operator ordinarily holds such a teach pendant by one handand performs operations for input keys by the other hand to teach themachines. In this case, the industrial robots or the NC machine tools asobjects to be taught (refer generally them to as a device, hereinafter)sequentially carry out operations respectively for steps in accordancewith a teaching operation. For example, a driving operation of a motor,a swing operation of an arm, an operation for turning on a work head(for instance, a welding gun) or the like are performed. At this time,the device may sometimes make an operation different from that intendedby the teaching operator owing to a mistake in teaching operation or thedefects of the parts of the device. In such a case, to avoid a danger tooperators in the vicinity of the device including the teaching operatorand prevent the device and peripheral devices from being broken, asafety system of the device needs to be constructed so that the teachingoperation is immediately inhibited or the device is quickly stopped.

Accordingly, in the usual teach pendant, at the time of the operationthat is not intended by the teaching operator as described above, anenable switch is employed so that the teaching operation is assuredlyinhibited and the device is immediately stopped. Further, the enableswitch is arranged at both sides of the teach pendant for the whip handof the teaching operator or for the purpose of improving the efficiencyof the teaching operation, and proposed and used so as to be operated byboth the hands.

Since muscles wither due to a surprise or an electric shock when adanger impends to a human being, for instance, the hands are heldtightly. Therefore, for the enable switch, a three-position switch of amomentary type is used. A state that the teach pendant is not gripped islocated at a below-described first operation.

To obtain a permitting state that the operation of the device ispermitted and an inhibiting state that the operation of the device isinhibited, a below-described enable contact signal of the three-positionswitch is outputted to the device. An enable contact is constructed soas to open to have the inhibiting state that the operation of the deviceis inhibited when a pressing-down stroke is operated to be located inthe first operating position smaller than a prescribed range and to belocated in a third operating position larger than the prescribed range,and so as to close to have the permitting state that the operation ofthe device is permitted when the pressing-down stroke is operated to belocated in a second position within the prescribed range. Further, whenthe enable contact is placed at the third operating position once, inthe second operating position where the pressing-down stroke ismitigated until the enable contact is placed at the first operatingposition, the enable contact is not closed to maintain the inhibitingstate that the operation of the device is inhibited.

For instance, the teaching operator may hold the teach pendant by a lefthand and carries out the teaching operation by a right hand, or viceversa. Further, in the teaching operation for a long time, byconsidering the fatigue of fingers or hands, the three-position switchesare arranged at two positions including a part which left fingers touchand a part which right fingers touch so that the teach pendant can bearbitrarily shifted from one hand to the other hand. The twothree-position switches can respectively permit the device to beoperated.

Further, the three-position switches are desirably constructed so thatwhen one three-position switch is located at the third operatingposition, the inhibiting state that the operation of the device isinhibited is established until both the three-position switches areplaced at the first operating positions, as proposed in Patent Document1 and patent Document 2.

Patent Document 1: JP-A-2002-355781

Patent Document 2: JP-A-2002-83522

In an embodiment disclosed in the Patent Document 1, when onethree-position switch is gripped and held at the second operatingposition, an enable contact is closed to obtain a permitting state thatthe operation of a device is permitted. Then, when the otherthree-position switch is operated to be located at the second operatingposition, the enable contact is opened to obtain an inhibiting statethat the operation of the device is inhibited. That is, only when onethree-position switch is placed at the second operating position, thepermitting state for permitting the operation of the device is obtained.

In an embodiment disclosed in the Patent document 2, when onethree-position switch is held at the second operating position, anenable contact is closed to obtain a permitting state that the operationof a device is permitted. Then, even when the other three-positionswitch is located at the second operating position, the permitting statefor permitting the operation of the device is maintained.

Ordinarily, the teaching operator grips the teach pendant by one handand carries out an operation for pressing down input keys by the otherhand to perform the teaching operation. Generally, in the teachingoperation for a long time, the operator has a chance to arbitrarilyshift the teach pendant from one hand to the other hand due to thefatigue of fingers or hands. An operating method during shifting theteach pendant from one hand to the other hand includes two methods of(1) that both the three-position switches are opened once to obtain thefirst operating positions and the other three-position switch isoperated to be located at the second operating position, or (2) thatboth the three-position switches are placed at the second operatingpositions and the other switch is opened to be located at the firstoperating position.

DISCLOSURE OF THE INVENTION

Problems that the Invention is to Solve

In the embodiment disclosed in the Patent document 1, according to theabove-described two operating methods, the inhibiting states arerealized once that the operation of the device is inhibited. Under theinhibiting state that the operation of the device is inhibited dependingon the structure or the use of the device, a driving power isinterrupted and driving energy is opened to ensure an assured safety.When the inhibiting state is established once, the driving power needsto be turned on and the driving energy needs to be accumulated until thepermitting state that the operation of the device is permitted issubsequently established and the device operates.

As described above, when the inhibiting state for inhibiting theoperation of the device is realized during shifting the teach pendantfrom one hand to the other hand, the driving energy needs to be openedand accumulated, so that problems of the loss of time and the loss ofenergy arise.

In the embodiment disclosed in the Patent Document 2, since both thethree-position switches are placed at the second operating position tobe located in the permitting states that the operation of the device ispermitted, the inhibiting state is not established according to theoperating method (2) for shifting the teach pendant from one hand to theother hand. However, when the teaching operator grips the teach pendantby both the hands owing to a surprise for an movement of the device thatis not anticipated while the teaching operator grips the teach pendantby one hand to perform the teaching operation, since the permittingstate remains that the operation of the device is permitted, a problemarises for a safety.

Thus, the present invention is proposed by considering theabove-described problems and it is an object of the present invention toprovide a control method for a teach pendant in which an operation canbe continuously carried out without interrupting the operation duringshifting the teach pendant from one hand to the other hand and a safetyis considered in the control method of the teach pendant used when anteaching of an operation or a simulation of the operation is carried outrelative to industrial robots or machine tools.

Means for Solving the Problems

For solving the above-described problems, there is provided with acontrol method for a teach pendant defined in claim 1, the teach pendantincluding: two three-position switches respectively having threeoperating positions of first operating positions, second operatingpositions and third operating positions in accordance with pressing-downstrokes, the three-position switch having: a detecting unit fordetecting the first operating position and the third operating positionto permit or inhibit the operation of a device in accordance with theoperating positions, the control method including:

a step of inhibiting the operation of the device, when both thethree-position switches are located at the second operating positionsfor a time exceeding a prescribed time.

There is provided with the control method for a teach pendant defined inclaim 2, wherein when both the three-position switches are located atthe second operating positions from the first operating positions, themeasurement of time is started, and while the measured time is smallerthan the prescribed time, when at least one of the three-positionswitches is located at the position of above-described other positions,the measurement of the time is stopped.

With such a structure, when the teach pendant is passed from, forinstance, from a left hand to a right hand, even in a series ofoperations that the two three-position switches provided in the teachpendant are firstly gripped by the left hand, and gripped by the righthand, and then, the left hand is opened, an inhibiting state that theoperation of the device is inhibited is not obtained and the teachpendant can be smoothly shifted from one hand to the other hand, so thata teaching operation can be continuously carried out.

When a teaching operator grips the teach pendant by both the hands owingto a surprise for the operation of the device that is not anticipated,the inhibiting state for inhibiting the operation of the device isestablished after the prescribed time to improve a safety.

In order to solve the above-described problems, there is provided with acontrol device for a teach pendant defined in claim 3, the teach pendantincluding: two three-position switches respectively having threeoperating positions of first operating positions, second operatingpositions and third operating positions in accordance with pressing-downstrokes, the three-position switch including: a signal processingcircuit having a detecting contact for detecting the first operatingposition and the third operating position to permit or inhibit theoperation of a device in accordance with the operating positions,wherein the signal processing circuit has detecting contact signals ofthe three-position switches as inputs to establish an inhibiting stateof the operation of the device when both the three-position switches arelocated at the second operating positions for a time exceeding aprescribed time, and to allow both the three-position switches to belocated at the first operating positions to cancel the inhibiting stateof the operation of the device.

According to this structure, even when one hand gripping the teachpendant is changed to the other hand, a permitting state that theoperation of the device is permitted is established, so that theteaching operation can be continuously carried out. Further, while boththe three-position switches are returned to the first operatingpositions, the permitting state in which the teaching operation can beperformed is prevented from being realized to improve the safety of theoperation of the teach pendant.

The control device for a teach pendant defined in claim 4 ischaracterized in that the signal processing circuit includes a circuithaving a relay.

Further, the control device for a teach pendant defined in claim 5 ischaracterized in that the signal processing circuit includes a circuithaving either a logic element or a logic operation element.

Still further, the control device for a teach pendant is characterizedin that the signal processing circuit is arranged in a teach pendantmain body or the device.

Accordingly, since the signal processing circuit can be easily formed byusing the relay, the logic element and the logic operation element and apart or an entire part of the circuit can be disposed in the device fromthe inner part of the teach pendant main body, the teach pendant grippedby the teaching operator can be miniaturized and light-weighted.

Advantage of the Invention

As described above, according to the control method for a teach pendantof the present invention, when one hand gripping the teach pendant ischanged to the other hand, the inhibiting state that the operation ofthe device is inhibited is not established so that the teachingoperation can be continuously carried out, and when the teachingoperator holds the teach pendant by both hands owing to a surprise forthe operation of the device that is not expected, the inhibiting statefor inhibiting the operation of the device is realized. Thus, the teachpendant with a high safety can be effectively provided.

BRIEF DESCRIPTION OF THE DRAWINGS

[FIG. 1] is a circuit block diagram of a first embodiment-for embodyingthe present invention.

[FIG. 2] is a state transition diagram of the first embodiment forembodying the present invention.

[FIG. 3] is a circuit block diagram of a second embodiment for embodyingthe present invention.

[FIG. 4] is a signal processing table of the second embodiment forembodying the present invention.

DESCRIPTION OF REFERENCE NUMERALS AND SIGNS

-   61 three-position switch for left hand-   62 three-position switch for right hand-   61-1, 61-2, 62-1, 62-2 operation detecting contact-   61-3, 62-3 third position detecting contact-   61-4, 61-5, 62-4, 62-5 enable contact-   63, 66, 68 relay-   64, 67, 69 resistor-   65, 70 condenser-   71 operation detecting line-   72 third operating position detecting line-   73 both switch operation detecting line-   81, 84 voltage converter-   82, 85 signal processing circuit-   83, 86 relay

BEST MODE FOR CARRYING OUT THE INVENTION

Now, specific embodiments of the present invention will be describedbelow by referring to the drawings.

FIRST EMBODIMENT

FIG. 1 a circuit block diagram of a first embodiment for embodying thepresent invention. Electric articles such as switches and relays forminga circuit are divided and arranged in a teach pendant not shown in thedrawing or the teach pendant and a device that is not illustrated.

Reference numeral 61 designates a three-position switch for a left handand has three operating states of a first operating position, a secondoperating position and a third operating position. Enable contacts 61-4and 61-5 close the circuit in the second operating position and open thecircuit in other positions than the second operating position. Operationdetecting contacts 61-1 and 61-2 as auxiliary contacts close the circuitin the first operating position and open the circuit in other positionsthan the first operating positions. Further, a third operating positiondetecting contact 61-3 as an auxiliary contact is provided that opensthe circuit in the third operating position and closes the circuit inother positions than the third operating position. Likewise, athree-position switch 62 for a right hand is equipped with operationdetecting contacts 62-1 and 62-2, a third operating position detectingcontact 62-3 and enable contacts 62-4 and 62-5.

The third operating position detecting contact 61-3 of thethree-position switch 61 for a left hand is connected in series to thethird operating position detecting contact 62-3 of the three-positionswitch 62 for a right hand. In the first embodiment, since a powersource has dc 24V, the other side of a relay 66 is connected to 0V andthe other part of the third operating position detecting contact 61-3 ofthe three-position switch 61 for a left hand is connected to the dc 24V(a description of connection to the dc 24V and 0V will be omittedhereinafter).

This circuit line is a third operating position detecting line 72 thatdetects the third operating position, since when at least onethree-position switch is placed at the third operating position, thethird operating position detecting contact of the three-position switchopens the circuit.

The operation detecting contact 61-1 of the three-position switch 61 fora left hand is connected in series to the operation detecting contact62-1 of the three-position switch 62 for a right hand to form anoperation detecting line 71 for opening the circuit when at least onethree-position switch is operated and the operation line detecting line71 is connected to a constantly opening contact 68 a of a relay 68.

The operation detecting contact 61-2 of the three-position switch 61 fora left hand is connected in parallel with the operation detectingcontact 62-2 of the three-position switch for a right hand to form aboth switch operation detecting line 73 for opening the circuit whenboth the three-position switches 61 and 62 are operated and the bothswitch operation detecting line 73 is connected to in series to aconstantly opening contact 63 a 3 of a relay 63. The both switchoperation detecting line 73 is connected in parallel with the other side(line 74) of the constantly opening contact 68 a of the above-describedrelay 68 connected to the operation detecting line 71, and then,connected in series to a constantly opening contact 66 a of a relay 66and the relay 63.

Form the line 74, a resistor 64 is connected in series to a condenser 65and connected to 0V. Further, a resistor 67 is connected in series to aconstantly closing contact 66 b of the relay 66 and connected inparallel with the condenser 65. When the line 74 is interrupted from thepower source 24V under a state in which the constantly opening contact66 a of the relay 66 closes the circuit, the condenser 65 is provided todelay the off-state of the relay 63 for a prescribed time (for instance,one second). The resistor 64 serves to limita current during storage tothe condenser 65 and protect a contact across which the stored currentis supplied. The constantly closing contact 66 b of the relay 66 servesto close the circuit when at least one three-position switch is placedat the third operating position to rapidly discharge electric chargestored in the condenser 65. The resistor 67 protects the constantlyclosing contact 66 b during the rapid discharge.

A constantly closing contact 63 b of the relay 63 is connected to therelay 68. A resistor 69 and a condenser 70 connected in series areconnected in parallel with the relay 68 to delay the off-state of therelay 68 for a prescribed time.

The enable contact 61-4 of the three-position switch 61 for a left handis connected in parallel with the enable contact 62-4 of thethree-position switch for a right hand, and connected in series to aconstantly opening contact 63 a 1 of the relay 63 and a constantlyclosing contact 68 b 1 of the relay 68 to form an enable contact outputsignal. Other enable contacts 61-5 and 62-5 are likewise connected inparallel with each other, and then, connected in series to a constantlyopening contact 63 a 2 of the relay 63 and a constantly closing contact68 b 2 of the relay 68 to form an enable contact output signal. In thisembodiment, the enable contact output signal has two systems, because aduplex circuit is formed not so as to harm the safety of a device, evenone is failed. In accordance with a request of a system that uses aparts material or a device with a sufficiently high reliability, onesystem may be adopted or three systems or more may be prepared for useof other purposes.

FIG. 2 is a state transition diagram in this embodiment and shows theoperating positions of the three-position switches and the permittingstate and the inhibiting state of the operation of the device. Anoperation of the circuit shown in FIG. 1 is described in accordance witha state transition of FIG. 2.

Initially, under a state that both the three-position switches 61 and 62are not operated, when the voltage 24V of the power source is turned on(state Pon), the third position detecting contacts 61-3 and 62-3 of thethree-position switches 61 and 62 close the circuit, so that the currentis supplied to the relay 66 connected thereto to excite and turn on therelay 66. On the other hand, since the initial state of the relay 63 isan off-state, the constantly closing contact 63 b of the relay 63 closedthe circuit, so that the relay 68 connected thereto is turned on. As aresult, the constantly opening contact 68 a of the relay 68 connected tothe operation detecting line 71 closes the circuit. At this time, sincethe three-position switches 61 and 62 are not operated, the operationdetecting contacts 61-1 and 62-1 close the circuit. Thus, the electriccurrent is supplied to the relay 63 to excite and turn on the relay 63and sore the condenser 65. As a result, the constantly opening contact63 a 3 of the relay 63 closes the circuit and the operation detectingcontacts 61-2 and 62-2 of the three-position switches also close thecircuit, so that a self-holding circuit to the relay 63 is formed. Whenthe relay 63 is turned on, the constantly closing contact 63 b thereofopens the circuit. Thus, the relay 68 is turned off. At this time, adischarge is carried out to the relay 68 from the condenser 70 for aprescribed time. Accordingly, even after the relay 63 is turned on, theoff-state of the relay 68 is delayed for a prescribed time to preventthe formation of the self-holding circuit of the relay 63 from beingfailed. After the prescribed time passes (after the discharge of thecondenser 70 is finished), the constantly opening contact 68 a of therelay 68 connected to the operation detecting line 71 opens the circuit.However, as described above, since the self-hold is established by thecircuit of the both switch operation detecting line 73 and theconstantly opening contact 63 a 3 of the relay 63, the on-state of therelay 63 is maintained.

Under this state, since the constantly opening contact 63 a 1 of therelay 63 and the constantly closing contact 68 b 1 of the relay 68 towhich the enable contacts 61-4 and 62-4 are connected close the circuit,the state of the enable contacts 61-4 and 62-4 becomes a stand-by statein which the enable contact output signal can be outputted. The enablecontact output signal of other enable contacts 61-5 and 62-5 can be alsooutputted.

Since both the three position switches 61 and 62 are not operated, theenable contacts open the circuit. Thus, an inhibiting state 1 (state 1)for inhibiting the operation of the device is established.

Now, an operation when the three-position switches 61 and 62 areoperated will be described below. Firstly, as an ordinary operation,when a teaching operator grips the teach pendant by one hand (forinstance, left hand), the operator presses down the three-positionswitch 61 for a left hand. As a result, the operation detecting contacts61-1 and 61-2 open the circuit. However, since the three-position switch62 for a right hand is not operated, the operation detecting contact62-2 closes the circuit and the self-hold of the relay 63 connectedthereto is established and maintained. Then, the teaching operator gripsthe teach pendant and the three-position switch 61 for a left hand isplaced at the second operating position, the enable switches 61-4 and61-5 close the circuit to output the enable contact output signal andobtain the permitting state 1 (state 2) for permitting the operation ofthe device.

During the operation of the device under the above-described permittingstate 1, when the operator strongly grips the three-position switch 61for a left hand due to a cause such as a surprise for the operation ofthe device that is not anticipated to place the switch at the thirdoperating position, the third operating position detecting contact 61-3of the three-position switch 61 for a left hand opens the circuit. Thus,the relay 66 connected thereto is turned off and the constantly openingcontact 66 a thereof opens the circuit. The relay 63 connected theretois also turned off so that the above-described self-hold is cancelled.As a result, the constantly closing contact 63 b of the relay 63 closesthe circuit and electric current is supplied to the relay 68 connectedthereto to excite and turn on the relay 68. The constantly openingcontacts 63 a 1 and 63 a 2 of the relay 63 and the constantly closingcontacts 68 b 1 and 68 b 2 of the relay 68 in the circuits of the enablecontact output signals open the circuits. Even when the enable contacts61-4, 61-5, 62-4 and 62-5 close the circuits owing to welding, theoutputs of the enable contact output signals are interrupted to have aninhibiting state 4 (state 3) for inhibiting the operation of the device.At this time, the electric charge stored in the condenser 65 isdischarged through the constantly closing contact 66 b of the relay 66closing the circuit.

When one hand gripping the teach pendant is changed to the other handduring the operation of the device in the above-described permittingstate 1, both the three-position switches 61 and 62 are placed at thesecond positions once, and then, the three-position switch 61 for a lefthand is released.

Firstly, when both the three-position switches 61 and 62 are placed atthe second operating positions, the operation detecting contacts 61-1,61-2, 62-1 and 62-2 open the circuit to interrupt the supply of power tothe operation detecting line 71 and the both switch operation detectingline 73. Thus, the condenser 65 begins to discharge to delay theoff-state of the relay 63 for a prescribed time. That is, the relay 63maintains an on-state and the relay 68 connected to the constantlyclosing contact 63 b thereof also maintains an off-state. Accordingly,since the constantly opening contacts 63 a 1 and 63 a 2 of the relay 63and the constantly closing contacts 68 b 1 and 68 b 2 of the relay 68 inthe circuits of the enable contact output signals keep closing thecircuits, the states of the enable contacts 61-4, 61-5, 62-4, and 62-5become a permitting state 3 (state 4) that the enable contact outputsignals are outputted to permit the operation of the device.

Then, when the three-position switch 61 for a left hand is released, theoperation detecting contact 61-2 closes the circuit so that the power issupplied to the relay 63 again to maintain the self-holding circuit tothe relay 63. At this time, the constantly opening contacts 63 a 1 and63 a 2 of the relay 63 and the constantly closing contacts 6 8 1 and 68b 2 of the-relay 68 in the circuits of the enable contact output signalskeep closing the circuits, and the states of the enable contacts 62-4and 62-5 closing the circuits become a permitting state 2 (state 5) thatthe enable contact output signals are outputted to permit the operationof the device.

When the above-described permitting state 3 is maintained, the relay 63is turned off for a prescribed time owing to the discharge of thecondenser 65, the constantly closing contact 63 b closes the circuit andthe relay 68 connected thereto is turned on. Since the constantlyopening contacts 63 a 1 and 63 a 2 of the relay 63 and the constantlyclosing contacts 68 b 1 and 68 b 2 of the relay 68 in the circuits ofthe enable contact output signals open the circuits, even when theenable contacts 61-4, 61-5, 62-4 and 62-5 of the three-position switches61 and 62 close the circuits, the outputs of the enable contact outputsignals are interrupted to have an inhibiting state 2 (state 6) forinhibiting the operation of the device.

From the above-described permitting state 3, for instance when theoperator strongly grips the three-position switch 62 for a right hand toplace the switch at the third operating position due to a cause such asa surprise for the movement of the device that is not expected, thethird operating position detecting contact 62-3 of the three-positionswitch 62 for a right hand opens the circuit, so that the power of therelay 66 connected thereto is interrupted to be turned off. Theconstantly opening contact 66 a opens the circuit to turn off the relay63 and turn on the relay 68 connected to the constantly closing contact63 b. Since the constantly opening contacts 63 a 1 and 63 a 2 of therelay 63 and the constantly closing contacts 68 b 1 and 68 b 2 of therelay 68 in the circuits of the enable contact output signals open thecircuits, even when the enable contacts 61-4 and 61-5 of thethree-position switch 61 closes the circuits, the outputs of the enablecontact output signals are interrupted to have an inhibiting state 8(state 7) for inhibiting the operation of the device. At this time, theelectric charge stored in the condenser 65 is discharged through theconstantly closing contact 66 b of the relay 66.

Even when the three-position switch 62 for a right hand is returned tothe second operating position from the above-described inhibiting state8, since the condenser 65 already performs a discharge so that thecondenser has no energy for turning on the relay 63 again even if thecondenser does not completely discharge. Thus, the relay 63 maintainsits off-state. At this time, the relay 68 is turned on to have theinhibiting state 2 (state 6) that the enable contact output signals arenot outputted to inhibit the operation of the device.

When the inhibiting state 2 to an inhibiting state 9 except theinhibiting state 1 (state 1) are established once, the constantlyopening contacts 63 a 1 and 63 a 2 of the relay 63 and the constantlyclosing contacts 68 b 1 and 68 b 2 of the relay 68 connected to theenable contact output signal circuits open the circuits. Thus, theenable contact output signals cannot be outputted. To close theconstantly opening contacts 63 a 1 and 63 a 2 of the relay 63 and theconstantly closing contacts 68 b 1 and 68 b 2 of the relay 68 connectedto the enable contact output signal circuits, both the three-positionswitches 61 and 62 need to be located at the first operating positionsand released. To place both the three-position switches 61 and 62 at thefirst operating positions means to completely open the operationdetecting contacts 61-1, 61-2, 62-1 and 62-2 thereof and the thirdoperating position detecting contacts 61-3 and 62-3. This state is thesame as that when the voltage 24V of the power source is initiallyturned on. As a result of the operations of the relays 63, 66 and 68,the constantly opening contact 63 a 1 of the relay 63 and the constantlyclosing contact 68 b 1 of the relay 68 to which the enable contacts 61-4and 62-4 are connected close the circuit so that the states of theenable contacts 61-4 and 62-4 become stand-by states that the enablecontact output signal can be outputted.

The enable contact output signal of the other enable contacts 61-5 and62-5 can be also outputted in the same manner as described above (state1).

For instance, as for a transition path from the inhibiting state 2(state 6) to the inhibiting state 1 (state 1), the three positionswitches 61 and 62 for left and right hands are kept released to placethe switches at the first operating positions. Depending on thedifference in timing for releasing the right and left hands, a path isused that the inhibiting state 2 (state 6) returns to the inhibitingstate (state 1) via an inhibiting state 3 or an inhibiting state 6.

As described above, when the teach pendant is shifted from one hand tothe other during the operation of keys by holding the teach pendant byboth the hands, the three-position switches are placed at the secondoperating positions once by both the hands. Then, even when one hand isreleased, the one hand gripping the teach pendant can be smoothlychanged to the other hand without making the operation of a robot to beinhibited. At this time, when at least one three-position switch isplaced at the third operating position due to a factor such as enencounter with a dangerous state, the operation is immediately shiftedto the inhibiting state so that the operation can be inhibited. Thus,the operation with a high safety can be realized.

Further, to detect the third operating position of at least onethree-position switch and assuredly interrupt the output of the enablecontact output signal and cancel the interruption, the return of boththe three-position switches to the first operating positions is detectedto close the output circuits of the enable contact output signals, thatis, cancel the interruption. Accordingly, when the outputs of the enablecontact output signals are interrupted once, the outputs of the enablecontact output signals can be assuredly interrupted irrespective of theshift timings of the states of the contacts due to switching of theoperating positions of the three-position switches or the shift timingsof the states of the contacts due to switching of on and off of therelays.

SECOND EMBODIMENT

Fig. is a circuit block diagram of a second embodiment for embodying thepresent device. This circuit is divided and provided in a teach pendantthat is not shown in the drawing or the teach pendant and a device thatis not illustrated like the first embodiment.

Reference numerals 61 and 62 designate three-position switches and arethe same as those of the first embodiment. Therefore, an explanationthereof will be omitted. In this embodiment, operation detectingcontacts 61-2 and 62-2 are not used.

Reference numerals 81 and 84 are voltage converters that input dc 24Vthrough auxiliary contacts of the three-position switches, convert thedc 24V to a dc 5V signal and output the dc 5V signal. In thisembodiment, a photo-coupler is employed and when the dc 24V is inputted,0V is outputted. When an input is 0V, 5V is outputted. The operationdetecting contacts 61-1 and 62-1 and the third operating positiondetecting contacts 61-3 and 62-3 of the three-position switches 61 and62 are connected to a power source of dc 24V in one side. They branch inparallel in the other side and are connected to the voltage converters81 and 84.

A signal output from the voltage converter 81 is connected to a signalprocessing circuit 82. A signal is processed in the signal processingcircuit 82 and a result is outputted to a relay 83.

Likewise, a signal out put from the voltage converter 84 is connected toa signal processing circuit 85. A signal is processed in the signalprocessing circuit 85 and a result is outputted to a relay 86. The relay83 and the relay 86 are connected to 0V in the other side.

The enable contact 61-4 of the three-position switch 61 for a left handis connected in parallel with the enable contact 62-4 of thethree-position switch 62 for a right hand and connected in series to aconstantly opening contact 83 a 1 of the relay 83 to form an enablecontact output signal.

Similarly, the enable contact 61-5 of the three-position switch 61 for aleft hand is connected in parallel with the enable contact 62-5 of thethree-position switch 62 for a right hand and connected in series to aconstantly opening contact 86 a 2 of the relay 86 to form an enablecontact output signal.

FIG. 4 shows a signal processing table of the signal processing circuits82 and 85 in this embodiment. In the drawing, contact states show inputsignals of the signal processing circuits 82 and 85. The contacts statesof the operation detecting contacts 61-1 and 62-1 and the third positiondetecting contacts 61-3 and 62-3 of the three-position switches 61 and62 indicate 0 in a circuit closing state, 1 in a circuit opening stateand “arbitrary” when no problem arises whether the circuit opens orcloses.

An inner state of the signal processing circuit indicates the innerstate of the signal processing circuits 82 and 85. An on-state isrepresented by 1, an off-state is represented by 0 and an state that maybe on or off state is represented by “arbitrary”.

When a controlling power is inputted to the signal processing circuits82 and 85, a power-on state shows 1. When the power-on state indicates1, a relay output is turned off (state 11).

When all the contact states 61-2, 61-3, 62-1 and 62-3 indicate 0, thepower-on state indicates 0 as an off-state. At this time, an inhibitiondetecting state and a timing state indicate 0 at the same time and atime excess state also shows 0 (state 12).

The inhibition detecting state sows 1 as an on-state when the contactstate 61-3 indicates 1 (state 17), the contact state 62-3 indicates 1(state 18) or a time elapse state shows 1 (state 16). When all thecontact states 61-1, 61-3, 62-1 and 62-3 indicate 0, the inhibitiondetecting state shows 0 as the off-state.

When the inhibition detecting state shows 1, the relay output is turnedoff.

The timing state shows 1 when the contact states 61-1 and 62-1 show 1and the contact states 61-3 and 62-3 indicate 0 (state 15). The timingstate shows 0 except the above-described states. That is, when both thetwo three-position switches are operated to be located at the secondoperating positions, the timing state shows 1 as the on state.

When the timing state indicates 1, the timing of a prescribed time isstarted. During the timing operation, when at least one of the twothree-position switches is located at the first operating position, thetiming state shows 0. When the timing operation is stopped, a timingvalue is cleared (state 12, state 13, state 14).

When the timing state indicates 1 and the prescribed time passes, thetime excess state shows 1 and the inhibition detecting state indicates 1as described above (state 16).

The relay output is turned on when the contact states 61-1 and/or 62-1indicate 1 and all the power-on state, the inhibition detecting stateand the time excess state show 0 (state 14, state 14, state 15).

A signal process in the signal processing circuits 82 and 85 will bedescribed in accordance with the operation of the teach pendant.

When a control power source is turned on, the power-on state indicates 1irrespective of an input state and the relay output is turned off (state11).

When both the three-position switches 61 and 62 are opened to place theswitches at the first operating positions, the contact states 61-1,62-1, 61-3 and 62-3 indicate 0 and the power-on state shows 0. At thistime, the relay output is turned off (state 12).

When the three-position switch 61 for a left hand is operated to belocated at the second operating position from the state 12, the contactstate 61-1 indicates 1 and the relay output is turned on (state 13).

When the three-position switch 62 for a right hand is operated to belocated at the second operating position from the state 12, the contactstate 62-1 indicates 1 and the relay output is turned on (state 14).

When both the three-position switches 61 and 62 are operated to belocated at the second operating positions, the relay output is turnedon, however, the timing state shows 1 to start a timing operation.

When one three-position switch 61 or 62 is released to be located at thesecond operating position from the state 15, the contact state 61-1 or62-1 indicates 0. At this time, the relay output maintains its on-state(state 13 or state 14).

When the state 15 is maintained, since the timing state indicates 1, thetiming operation progresses. When a prescribed time passes, the timeexcess state shows 1 and the inhibition detecting state also shows 1. Atthis time, the relay output is turned off (state 16).

When at least one three position switch 61 or 62 is placed at the thirdoperating position from any of the states during an ordinary teachingoperation, the contact state 61-3 or 62-3 indicates 1 and an inhibitingstate of 1 is established. At this time, the relay output is turned off(state 17 or state 18).

When both the three-position switches 61 and 62 are opened to place theswitches at the first operating positions from the states 16, 17 and 18having the inhibition detecting state of 1, the contact states 61-1,62-1, 61-3 and 62-3 indicate 0, and the inhibition detecting state, thetiming state and the time excess state show 0. The relay output at thistime is turned off (state 12).

In this embodiment, the signal process in the signal processing circuits82 and 85 is described. The signal processing circuits 82 and 85 may bereadily realized by combining logic elements on the basis of theabove-description. Further, when a logic operation element such as a CPUis employed to perform the signal process, the same effects can berealized.

INDUSTRIAL APPLICABILITY

The present invention is applied to a safety device when an operatorcomes near to an automatic machine operating in accordance with thepower of a motor or to an operating switch for instructing the operationof the automatic machine, so that the safety of the operator can beensured and the reliability of the device can be improved.

1. A control method for a teach pendant, the teach pendant including:two three-position switches respectively having three operatingpositions of first operating positions, second operating positions andthird operating positions in accordance with pressing-down strokes, thethree-position switch having: a detecting unit for detecting the firstoperating position and the third operating position to permit or inhibitthe operation of a device in accordance with the operating positions,the control method comprising: a step of inhibiting the operation of thedevice, when both the three-position switches are located at the secondoperating positions for a time exceeding a prescribed time.
 2. Thecontrol method for a teach pendant according to claim 1, wherein whenboth the three-position switches are located at the second operatingpositions from the first operating positions, the measurement of time isstarted, and while the measured time is smaller than the prescribedtime, when at least one of the three-position switches is located at theposition of above-described other positions, the measurement of the timeis stopped.
 3. A control device for a teach pendant, the teach pendantincluding: two three-position switches respectively having threeoperating positions of first operating positions, second operatingpositions and third operating positions in accordance with pressing-downstrokes, the three-position switch including: a signal processingcircuit having a detecting contact for detecting the first operatingposition and the third operating position to permit or inhibit theoperation of a device in accordance with the operating positions,wherein the signal processing circuit has detecting contact signals ofthe three-position switches as inputs to establish an inhibiting stateof the operation of the device when both the three-position switches arelocated at the second operating position for a time exceeding aprescribed time, and to allow both the three-position switches to belocated at the first operating positions to cancel the inhibiting stateof the operation of the device.
 4. The control device for a teachpendant according to claim 3, wherein the signal processing circuitincludes a circuit having a relay.
 5. The control device for a teachpendant according to claim 3, wherein the signal processing circuitincludes a circuit having either a logic element or a logic operationelement.
 6. The control device for a teach pendant according to claim 3,wherein the signal processing circuit is arranged in a teach pendantmain body or the device.